1. Field of the invention:
The present invention relates to an interlinking control device for operating a brake and a clutch with a single pedal in a tractor-mounted working machine on which an engine with a governor is mounted.
2. Description of the Prior Art:
Tractor-mounted working machines having various working units such as lawn mowers, cultivators, snowplows, for example, generally employ a single engine for driving both drive wheels and the working unit. In order to permit the working unit to perform its intended operation reliably, the engine is equipped with a governor for controlling the engine to rotate at a constant speed against load variations. The engine with the governor produces a drive force even when the tractor is braked since the braking force is regarded as a load by the governor. Therefore, the tractor cannot be stopped until the braking force exceeds the output power of the engine at a predetermined speed of rotation of the engine.
In general, the tractor-mounted working machines of the type described above include a brake control system and a clutch control system which are operatively interconnected by a single pedal for operating the brake and the clutch in interlinked relation. As shown in Japanese Utility Model Publication No. 47-10085 published on Apr. 15, 1972, one such a brake and clutch interlinking arrangement is designed such that, when the pedal is depressed, the clutch is first disconnected and then the brake is actuated. When the tractor is braked after the clutch has been disengaged, the tractor tends to be braked abruptly because the braking force sharply increases in a short pedal stroke near the end of the entire depression stroke of the pedal. In case the tractor is to be stopped on an uphill road, the tractor may back off before the brake develops a sufficient braking force. Another problem is that when the pedal is released to start the tractor after it has been braked by the pedal, the clutch is then engaged with no braking force on the tractor, causing the tractor to start suddenly and quickly.